Prosthetic devices, such as prosthetic limbs, are typically lightweight components that replace damaged or missing body parts of a particular patient. Many prosthetic devices are subject to significant forces applied via complex, variable motions of the surrounding body parts. Selected sites on prosthetic devices are accordingly reinforced to withstand particularly large loads. However, reinforcing selected sites on leg sockets and other devices without increasing the weight and cost of the devices is difficult.
FIG. 1A is an exploded isometric view of a conventional leg socket 10 that may be attached to a leg stump S of a particular patient P. The socket 10 typically has a lightweight liner 12 composed of a thermoplastic or fiberglass sheet that is shaped to fit the contour of the leg stump S. The leg socket 10 may also have a connector assembly 20 having a base 22, a plurality of fingers or legs 24 projecting from the base 22, and an inverted pyramid 26 projecting from the base 22. The connector assembly 20 is generally a rigid metal component attached to the distal end of the liner 12, and the inverted pyramid 26 is configured to engage a mating adapter on a pylon (not shown). Other connector assembly structures may, of course, be used, and an outer shell (not shown) is typically laminated over the liner 12 and the legs 24.
FIG. 1B is a partial isometric view of the connector assembly 20 attached to the liner 12 of the leg socket 10. To attach the connector assembly 20 to the liner 12, a prosthetist manually deforms the legs 24 of the connector assembly 20 to roughly fit the liner 12. The prosthetist, for example, generally bends the legs 24 downwardly from the base 22 and hammers selected points along each leg 24 to roughly fit each leg 24 to the particular area on the liner 12. After the legs 24 are deformed to roughly fit the particular geometry of the liner 12, the legs 24 are secured to the liner 12 with a plurality of fasteners 28. The prosthetist then laminates an outer sheet of fiberglass (not shown) to the legs 24 and the liner 12 with a resin binder to form the leg socket 10.
Reinforcing the leg socket 10 with the connector assembly 20 generally increases the costs and reduces the performance of the prosthetic limb. For example, attaching the connector assembly 20 to the liner 12 is extremely time-consuming because the prosthetist manually deforms each of the metal legs 24 with a hammer to fit the geometry of the liner 12. Additionally, attaching the connector assembly 20 to the liner 12 is also imprecise because the legs 24 may not accurately conform to depressions 18 (shown exaggerated) or other topographical features on the surface 16 of the liner 12. Many leg sockets 10 with metal connector assemblies 20 are thus subject to significant point loading at various locations between the legs 24 and the liner 12 or outer fiberglass layer (not shown). As a result, the thickness of the liner 12 and the subsequent outer fiberglass layer are increased to sustain the point loading caused by the connector assembly 20. It will be appreciated that the significant time requirements and additional materials increase the weight and cost of the leg socket 10.
FIG. 2A is a partial isometric view of another conventional leg socket 10a with an liner 12 and a connector assembly 20a connected to the liner 12. The connector assembly 20a has a plurality of cables 24a extending from the base 22. In operation, the prosthetist lays the cables 24a over the surface 16 of the liner 12 and laminates an outer sheet of fiberglass (not shown) over the liner 12 and the legs 24a. The connector assembly 20a does not require as much time to install as the connector assembly 20 shown in FIG. 1B because the prosthetist does not need to hammer each of the cables 24a to fit the geometry of the liner 12. The connector assembly 20a, however, may produce significant point loading along the cables 24a because each cable 24a transmits forces to discrete, isolated areas of the liner 12 and the outer fiberglass layer. Moreover, most of the force applied to the connector assembly 20a acts against the resin and the outer fiberglass layer because the cables 24a are not fastened to the liner 12 and the cables 24a act separately from the resin. Therefore, it is also necessary to make the socket 10a with substantially thick walls in the region of the connector 20a to withstand the forces generated in typical installations.
FIG. 2B is a partial isometric view of yet another conventional leg socket 10b with another connector assembly 20b attached to the liner 12. The connector assembly 20b has a base 22b with first and second slots 23 and 25 extending perpendicular to one another across the top of the base 22b. A first strip 24b.sub.1 positioned in the first slot 23 projects from a first set of opposing sides of the base 22b, and a second strip 24b.sub.2 positioned in the second slot 25 projects from a second set of opposing sides of the base 22b. The prosthetist attaches the connector assembly 20b to the liner 12 by positioning the strips 24b.sub.1 and 24b.sub.2 in the slots 23 and 25, and then laminating an outer sheet of fiberglass over the base 22b, the strips 24b.sub.1 and 24b.sub.2, and the liner 12. A separate pylon connector 30 with a pyramid 32 is then attached to the base 22b. The connector assembly 20b also reduces the installation time compared to the metal connector assembly 20 because the prosthetist can more easily deform the strips 24b, and 24b.sub.2 to conform to the geometry of the liner 12. However, as with the connector assembly 20a shown in FIG. 2A, the connector assembly 20b also produces point loading in the resin binder, the fiberglass outer sheet, and the liner 12. As a result, the leg socket 10b also has thick walls in the region of the connector assembly 20b.